Nowadays, there is an increasing interest to replace conventional incandescent bulbs with LEDs (light emitting diodes). Nevertheless, how to make LED driving apparatus be compatible with dimmers in existing lighting apparatuses becomes a challenge.
The most common type of dimmers is phase cut dimmer including leading edge dimmer and trailing edge dimmer, wherein the main supply is cut off for part of the main cycle. In some situations, the dimmer has been removed so there is no dimmer. To sum up, there are three different dimming conditions: leading edge dimming, trailing edge dimming and no dimming. The working principles of these three dimming conditions are so different that the LED driving apparatus needs to distinguish the dimming conditions and work in different operation modes accordingly. Otherwise, its performance will suffer and a flicker may happen.
The existing solutions of dimming mode detection are few and generally based on digital technology, which is complicated and high cost. Therefore, there is an ongoing need to find an effective and easy way to detect the dimming mode.